/*
 * Copyright (c) 2019 - now, Eggroll Authors. All Rights Reserved.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.webank.eggroll.core.retry.impl.waittime;

import com.google.common.base.Preconditions;
import com.webank.eggroll.core.retry.AttemptContext;
import com.webank.eggroll.core.retry.WaitTimeStategy;
import javax.annotation.concurrent.Immutable;

@Immutable
public final class ExponentialWaitTimeStrategy implements WaitTimeStategy {

  private final long multiplier;
  private final long maxWait;

  public ExponentialWaitTimeStrategy(long multiplier, long maxWait) {
    Preconditions.checkArgument(multiplier > 0, "multiplier must > 0");
    Preconditions.checkArgument(maxWait >= 0, "max wait must >= 0");
    Preconditions.checkArgument(multiplier < maxWait, "multiplier must < max wait");

    this.multiplier = multiplier;
    this.maxWait = maxWait;
  }

  @Override
  public long computeCurrentWaitTime(AttemptContext<?> failedAttemptContext) {
    long exp = 1 << (failedAttemptContext.getAttemptCount() - 1);
    long result = multiplier << exp;

    return result <= maxWait ? result : maxWait;
  }
}
